In Heavy Going, Part One I shared a British pilot’s impressions of flying the RAF’s “American heavies” during World War Two.

However it’s never easy to understand which B-17 and B-24 models the British used when. They didn’t simply follow the American alphabetical system, and the Mark numbers they did use were largely assigned in the order that the purchase agreements crossed some overworked Whitehall clerk’s desk.

Still, an outline of both bombers’ RAF careers can framed by working through their service designations – a Gordian Knot I shall now attempt to unravel before your very eyes…

Fortress I: Too little, too soon

In 1940, Britain knew it needed heavy bombers to take the war to Hitler’s doorstep. And almost as soon as the US Government enacted Lend-Lease on March 11th, 1941 the British managed to convince a reluctant USAAC to give them 20 B-17Cs (from a batch of just 38) fresh off Boeing’s Seattle line – starting with #40-2043.

I’m sure the term ‘combat assessment’ would have been leveraged.

Anyway, they were assigned British serials AN518 to AN537, but Boeing mistakenly marked them all as “AM”. To further confuse us, the numbers were all fixed later.

The American aircraft were then given self-sealing fuel tanks, Sperry 0-1 bomb sights, and British radios before entering RAF service as the Fortress I. They weren’t a big success. Between July 8th and the end of September 1941, only 39 sorties had been launched for 8 losses, 18 mechanical aborts and 2 other diverted attacks caused by mechanical problems.

The Air Ministry told the USAAC that the B-17C was simply not combat ready – it couldn’t handle the cold, the altitude or the Luftwaffe. The RAF abandoned daylight bombing forthwith, and sent four Fortress Is to the Middle East and at least five more to Coastal Command for convoy patrol.

Fortress II: If at first you don’t succeed…

No doubt expecting better things, the RAF had already ordered 300 of the much-improved B-17F. However the Japanese attack on Pearl Harbor meant the USAAC needed more bombers urgently. So the RAF was sent 46 B-17Es from USAAC inventory in August 1942 and these entered service as the Fortress IIA. Ordered first but delivered second, a further 19 new-built B-17Fs would be designated Fortress II.

However the British now had their own heavy bombers in service and were much less impressed by the B-17’s smaller bomb load. They were also still gun-shy after the Fortress I experience, so the Fortress IIAs and IIs were sent straight to Coastal Command for ocean patrol, where they were re-designated the Fortress GR.II (for ‘General Reconnaissance’) and GR.IIA.

With their long range, ASV (air to surface vessel) radar and depth charges, they proved quite successful in this role, destroying 13 U-boats before they were replaced by even longer-legged Liberators and Short Sunderland flying boats.

Fortress III: Electronic arsenal

In early 1944, the RAF received another 14 B-17Fs from the USAAF, which were converted into electronic warfare ships designated Fortress II (SD) where SD stood for ‘Special Duties.

These were mainly used as trainers for electronic warfare Fortress III(SD)s, which were specially equipped B-17Gs. They carried an array of high tech including Monica Mark IIIA tail-warning receiver; Jostle Mark IV VHF jammer, AN/APS15 radar, Airborne Cigar radio jamming,  Airborne Grocer air-intercept radar jammers; Gee and LORAN navigation; ‘window’, and H2S bomb-aiming radar. Some even carried a German-speaking operator who would jam and misdirect Luftwaffe night fighters.

The remaining Fortress IIIs were used for convoy and met patrol over the Atlantic, as well as in other bomber support roles on large RAF night raids.

In all, the USAAF transferred 85 Fortress IIIs/B-17Gs – 30 Boeing-built planes marked as HB 761 to HB 790; and 55 built by Lockheed-Vega with serials HB791/793, 795, 796, 799/803, 805, 815/820, KH998, KH999, and KJ100/127, KL830/837. However 13 were diverted back to the USAAF before they could be delivered.

Liberator: Available in numbers

Now let’s go back to June 1940, when the French placed an order for 175 early Consolidated Liberators, to be known as the LB-30MF. This anachronistic designation referred to ‘Land Bomber’, model 30 (as it was to be derived from the XPB3Y long range patrol bomber flying boat concept, shown to the French in 1938), and ‘Mission Français’.

Within weeks, however, France no longer had any need for a strategic bombing capability and, as arranged earlier, the British took over their aircraft orders. The design was tweaked to include standard RAF equipment, self-sealing tanks, no fewer than fourteen Browning .303 machine guns, Boulton-Paul electric turrets, Curtiss-Electric propellers and a three-foot nose extension.

After various discussions, the British finally ordered 140 of this unique model, which had no equivalent in US service, and called it the LB-30 Liberator Mk.II – even though the Liberator was Consolidated’s Model 32. Serialled AL503 to AL667 the first, AL503, was lost on its acceptance flight when a loose bolt jammed the elevator controls. The bomber dove into San Diego Bay killing all on board, including Consolidated’s chief test pilot William Wheatley.

The balance of the contract was made up with six YB24s originally ordered by the USAAC and designated LB-30A Liberator Mk.IA (with RAF serials AM258 to AM263); plus another 20 B-24As which were diverted from the USAAC’s initial order of 38 airframes, given RAF serials AM910 to AM929, and called LB-30B Liberator Mk.IB.

Liberator II: Needs of empire

As with the RAF Fortresses, deliveries began in March 1941. The YB-24/LB-30As were first to arrive, but they didn’t have superchargers or self-sealing tanks and were instantly deemed unfit for combat. Instead, they were used as unarmed transports by the Atlantic Return Ferry Service, along with BOAC and, later, QANTAS Empire Airways.

Three of the twenty LB-30B Liberator Mk.Is also went to transport duties, two were lost in accidents,  and the rest went to No.120 Squadron of RAF Coastal Command and conducted anti U-boat patrols through the Battle of the Atlantic.

At the same time, the original LB-30MFs started arriving in the UK as LB30 Liberator Mk.IIs. Most would see service as bombers in the Middle and Far East, although several more would join BOAC for transport and trans-Atlantic ferry duties.

The second LB-30 (AL504) was converted into Winston Churchill’s personal VIP transport, in a natural metal finish..

However, by now the US was at also war and desperately needed long range B-24s in the Pacific. So of the 139 Liberator Mk.IIs ordered (accounting for the loss of AL503), 73 were taken over by the USAAC and designated LB-30A – the LB was given to mean ‘Liberator to British specification’. As a result, only 64 made it to the RAF. Later, the USAAF would ‘return’ 23 of their LB-30s to RAF service.

Liberator III: The first of many

The RAF would go on to use large numbers of the vastly-produced B-24 – on convoy and ASW patrols in the Atlantic, and in the Far East as long range bombers, cargo and special ops planes. They never used it for large scale bombing in Europe but, like the Fortress III, they did load a number of later Liberators with electronic jamming equipment and fly them as night bomber support.

The Liberator B (for Bomber) Mk.III was next in line, and 366 of them would eventually complement 37 RAF squadrons. These were the mass-produced B-24D with their added tankage, guns and numerous other (ongoing) improvements, purchased before Lend-Lease came into effect. The British specified .303 Brownings throughout, British radios, etc, and a Boulton-Paul powered turret bearing four .303 guns in the tail.

But just as things started to get simple, USAAF B-24s became available under Lend-Lease and the RAF was able to receive more of them. All Lend-Lease aircraft would be standard American machines from USAAF production orders. The first of the many were 11 further B-24Ds – serials LV336 to LV346 – which were transferred from the USAAF in March and April of 1942 after a direct request from Churchill. Because of their American fit-out, they were identified as the Liberator B.Mk.IIIA once they’d crossed the Atlantic.

Even more confusing was the Mark IIIB, which was temporarily applied to Coastal Command’s ASV-equipped convoy patrol aircraft, before they were re-tagged as the Liberator GR.Mk.III (the GR standing for General Reconnaissance).

Liberator IV and V: Extending the range

Somewhat surprisingly, the B.Mk.III was followed by the B.Mk.IV, an anglicised version of the B-24E being built by Consolidated, Douglas Tulsa, and as the first model to come out of Ford’s Willow Run plant. In the end (and probably due to the problems at Willow Run) they were never delivered, but the RAF managed to save some ink by re-using the B.Mk.IV designation for a handful of Mk.VI conversions. (Exactly how these Mk.VIs were altered, I haven’t been able to find out).

Coastal Command then claimed the Mk.V designation, by adding a mix of chin radar, retractable ventral radar, ASV arrays, a Leigh Light, extra fuel and various other bits of ASW equipment to their Mk.III / B-24Ds. More accurately, these modified Mk.IIIs became the Liberator GR.Mk.V.

At the same time, a Liberator B.Mk.V was evolving from the B-24D-based B.Mk.III, using the same armament but replacing the weight of armour with extra fuel capacity.

And then there was the Liberator C Mk.V, which was a later transport conversion of the GR.Mk.V.

Whether or not the Mk.III and Mk.IIIA differences figured into all these conversions and designations is a little unclear.

Liberator VI – IX: You name it

B-24Gs, essentially the B-24D produced by North American Aviation, were known as the Liberator B.Mk.VI in RAF service. These were followed into service, confusingly, by the B.Mk.VIII which was the RAF designation for the virtually identical B-24H and B-24J, as well as a number of B-24Ls built by Ford. In all, around 1,600 Mk.VI and Mk.VIII Liberators would fly for England.

Even the clerks in Whitehall seemed to be losing track at this point, and there’s no clear correlation between the British Marks and their American origins. B-24Gs, Hs, and Js were sometimes identified as B.Mk.VI, while Mk.VIII generally (but not universally) applied to the later deliveries. In the US, the Liberator plants were moving from the original Emerson A-15 nose turret to Consolidated A-6 units through these models, so perhaps that was the deciding factor.

Coastal Command then clouded the waters even more by creating the GR.Mk.VI, which was a Very Long Range B Mk.VI with centimetric ASV radar in place of the ventral turret; and the GR.Mk.VIII which was a B-24J with the same ASW modifications but ventral H2X radar instead of the ASV unit.

Between the various Mk.VIs and Mk.VIIIs (you noticed this was missing, right?) came the C.Mk.VII, which was the dedicated C-87 cargo version of the Liberator, or Liberator Express. The British received 24 of these freighters under Lend-Lease, built from B-24D airframes at Convair Fort Worth and given the RAF serials EW611 – EW634.

Of course, the ever-resourceful RAF also converted some of its B.Mk.VIs and GR.Mk.VIs to cargo carrying as well, and thoughtfully re-designated them all as C.Mk.VI. A similar path followed for a number of Mk.VIIIs, which became cargo carrying C.Mk.VIIIs.

And finally, there was the Liberator C.Mk.IX, a cargo version based on the USN Privateer/RY-3, sporting a taller single tail fin, lengthened fuselage and rotated engine cowlings so the familiar oval was longer in the vertical axis with cooling intakes above and below, rather than at the sides.

And that’s the family

While things certainly got simpler as the Liberator’s design matured and deliveries stabilised (as they did with the Fortress), the British numbering system will always make identifying their B-17s and B-24s more challenging for me than it could ever have been for an Axis fighter pilot!

Along with the RAF and RCAF, the Royal Australian Air Force was a prolific Liberator user. In all, seven squadrons (plus an Operational Training Unit and two special ops flights) operated several hundred Lend-Lease B-24s between 1944 and 1948. But despite using a mix of B-24D, J, L and M models, they were all grouped under the one ‘A72’ type prefix – and the original American model designations were only used at a functional level. Simples.

Anyway, I hope things are a little clearer now.

 

Written with huge thanks to Air Vectors and Joe Baugher’s Military Aircraft Serials.
And be sure to explore more of the Imperial War Museum’s Fortress and Liberator image collections.